The present invention relates to a data recording apparatus and the method thereof and, more particularly, an approach method for recording vehicle data including control parameters in a control unit equipped in a vehicle.
In the prior art, in order to identify faulty conditions of the vehicle, known is the data recording apparatus for downloading the control parameters of the control unit equipped in the vehicle, and then recording such parameters. For example, disclosed in JP-A-2002-070637 is the data recording apparatus for efficiently recording the data of the control unit without a fail by utilizing effectively a limited memory capacity. In the data recording apparatus of JP-A-2002-070637, various data (i.e., the control parameters) in the control unit on the vehicle side are sampled on a time-series basis, and then acquired sampling data are stored in an SRAM as required. Then, when satisfied are predetermined trigger conditions equivalent to the conditions under which the data that are useful for identifying the faulty condition of the vehicle will be obtained, a series of the sampling data stored in the SRAM are downloaded, and then such data are stored in the data recording unit. However, in the data recording apparatus of JP-A-2002-070637, since the sampling of the control parameters is restricted by a time, such sampling of the control parameters is stopped temporarily while the sampling data are stored in the data recording unit.
According to the prior art described above, such data cannot be acquired due to the above periodical restriction even though the data are useful for identifying the faulty condition of the vehicle. Such a situation will be produced in the case where the subsequent trigger conditions are satisfied once again while previous data are still being downloaded in the data recording unit after the preceding trigger conditions are satisfied. In this case, the sampling itself of the control parameters is interrupted forcedly owing to the satisfaction of the preceding trigger conditions. Therefore, even if the subsequent trigger conditions are satisfied in the middle of this interruption, the sampling data themselves cannot be acquired, and of course such data cannot be stored in the data recording unit. As a result, when the trigger conditions are satisfied successively, the recording failure of the necessary data will occur, and therefore reduction in a reliability of the recorded data will be brought about.